1. Field of the Invention
This invention relates to electronic sockets, and more particularly, to electronic circuit module test sockets for temporarily contacting modules with a combination of pins and pads on the bottom surface that must be contacted simultaneously.
2. Description of Related Art
In the process of manufacturing multi-chip integrated circuit (IC) modules, it is necessary to temporarily make contact to the electrical interface connections (commonly called "pins" or "I/Os") for the purpose of characterization and test. As these devices have become increasingly more dense and complex, the number of I/O connections to a system have also increased, to the point of some multichip modules having hundreds or even thousands of I/Os. Earlier devices with fewer I/Os often had these I/Os arranged around the periphery of the package, and they were easily placed into and removed from a socket with a reasonable amount of force. The more complex devices now have large area arrays of contacts, and the forces required to insert and remove a device have become considerable, with increased risk of damage to the device, contact socket, or tester interface board.
This problem led to the development of low-insertion-force (LIF) and zero-insertion-force (ZIF) sockets for devices with pins (Pin Grid Array or PGA), and spring contact compression sockets for devices without pins (Land Grid Array or LGA). The prior art includes many different implementations of these two general contacting methods, each implementation having certain advantages and disadvantages for a particular contacting situation.
Some examples of prior art zero insertion force (ZIF) sockets for contacting PGA devices are found in U.S. Pat. No. 5,057,031 to Sinclair; U.S. Pat. No. 4,468,072 to Behzadi; U.S. Pat. No. 4,674,811 to Corwin; U.S. Pat. No. 4,836,798 to Carter; U.S. Pat. No. 4,889,499 to Socher; U.S. Pat. No. 5,123,855 to Peterson; U.S. Pat. No. 5,002,499 to Matsuoka; U.S. Pat. No. 4,498,725 to Bright et al.; U.S. Pat. No. 5,609,495 to McHugh; U.S. Pat. No. 5,092,789 to Sinclair; U.S. Pat. No. 5,108,302 to Pfaff; U.S. Pat. No. 4,496,205 to Christensen et al.; and U.S. Pat. No. 4,422,703 to Christensen et al. These sockets, while suitable for their intended use, cannot contact a module with both pins and pads incorporated in the module design.
Some examples of prior art spring contacts and sockets with arrays of spring contacts for contacting LGA devices are found in U.S. Pat. No. 4,502,747 to Bright et al.; U.S. Pat. No. 5,215,472 to DelPrete et al.; U.S. Pat. No. 4,636,026 to Cooney et al; U.S. Pat. No. 5,127,837 to Shah et al; U.S. Pat. No. 4,397,519 to Cooney; U.S. Pat. No. 5,151,040 to Tanaka; and U.S. Pat. No. 4,358,175 to Reid. These contacts and sockets, while suitable for their intended use, cannot contact a module with both pins and pads incorporated in the module design.
An example of a prior art socket that is configurable for either PGA or LGA (by exchanging some component parts) is found in U.S. Pat. No. 5,395,254, Mogi. While this socket contacts PGA and LGA, it cannot contact both simultaneously, and is also not suitable for a large number of contacts.
A specific design ZIF socket for PGA modules with many pins having some unique properties is described by R. G. Meeker of IBM East Fishkill, N.Y. in IBM Technical Report No. TR22.2141, "ETT Zero Insertion Socket".
Commercially available contacting sockets do not provide any suitable solutions to the aforementioned problems.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a system to provide repeatable electrical continuity simultaneously between an IC with different I/O arrays and a load board attached to a test system or any other electrical peripheral devices.
It is another object of the present invention to provide such a system which also performs all the critical components of any IC interconnect contact, i.e., actuation, alignment, retention and release.
A further object of the invention is to provide such a system which also includes easy reparability of individual contacts for the different contact parts of the socket.
It is yet another object of the present invention to provide an assembly for connecting an IC to a load board which permits simultaneous connection of the test connectors on the IC and the production I/O pins, with zero or low insertion force.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.